The present invention relates to circuit breakers, more particularly to circuit breakers for promoting current-limiting effect and improved breaking performance.
Generally, in some conventional circuit breakers, electromagnetic means are adapted to operate a trip-free mechanism by the working of the electromagnet for momentary tripping at first, and then to forcibly open a contact arm with the remaining stroke of the electromagnet. However, in such circuit breakers, the movable contact is normally biased by a pressure means such as a compression spring in which the rate of increase of force is normally remarkably high, when the contact arm is forced to open. Therefore the opening force is not enough and it is impossible to get sufficient distance by the action of the electromagnet alone. Accordingly, after some time delay by an operation of switching mechanism, the circuit breaker effectively begin to open the contact with the co-operatio of the trip-free mechanism and the forcibly operating electromagnet means.
But a problem exist in that the breaking time tend to become longer.